1. Field of the Invention
The present invention relates to a steering angle detection device for an electric power steering apparatus.
2. Description of the Related Art
Japanese Patent Publication Laid-Open No. 2001-194251 (page 3 and FIGS. 2 and 3) discloses a steering angle detection device for an electric power steering apparatus. The electric power steering apparatus is configured such that a first shaft of a torque sensor that detects a steering torque applied to a steering wheel is coupled to a steering wheel shaft connected to a steering wheel, and a second shaft of the torque sensor, which is coupled to the first shaft via a torsion bar, is coupled to a steered vehicle wheel via a steering gear. Rotation angles of the first and second shafts are detected by first and second resolvers, and the steering torque is derived from the rotation difference of the first and second shafts that is detected by the first and second resolvers. An electric motor then applies assistance force that is derived from the steering torque to the steering gear. The steering angle detection device for this electric power steering apparatus is configured such that a steering angle of the steering wheel that can rotate multiple times to the left or right from a straight ahead position is detected based on detection signals from the first and second resolvers, and a multiple-turn absolute detection unit provided on the second shaft.
However, in the steering angle detection device for the electric power steering apparatus described above, the multiple-turn absolute detection unit, which detects a rotation number of the steering wheel shaft coupled to the steering wheel from the straight ahead position, has to be provided additionally. This causes problems related to cost increase and the need for installation space.